Herb of Grace

Rue is so called because of its use in exorcism, and hence the
Roman Catholics sprinkle holy water with a bunch of rue. It was for
centuries supposed to prevent contagion. Rue is the German raute;
Greek, rute; Latin, ruta, meaning the “preserver,” being
a preservative of health (Greek, ruo, to preserve). Ophelia
calls it the “Herb of Grace o' Sundays.”